The Role of Dynamic ctDNA Monitoring During Combination Therapies of BRAF V600E-Mutated Metastatic Colorectal Cancer: A Case Report.

Background: BRAF V600E mutation represents a group of colorectal carcinoma with poor prognosis. Although treatment strategies have been recommended after clinical investigations, the progression-free survival is short and unsatisfying.

Case Presentation: Here, we present the case of a 28-year-old male diagnosed with ascending colon adenocarcinoma with multiple liver metastases. Treatment with FOLFIRI plus cetuximab and vemurafenib achieved partial response, following which the patient received conversion surgery with clear resection margin. After disease recurrence, he received combination treatment of nivolumab and regorafenib. Until August 2020, the patient achieved a partial response with more than 12 months progression-free survival. Circulating tumor DNA (ctDNA) was monitored during the patient's treatment. His ctDNA fractions exhibited significant elevation two months before disease progression. As a comparison, the tumor markers were not elevated until the patient was confirmed PD through CT imaging.

Conclusion: This case exemplifies how liquid biopsy and ctDNA sequencing can aid in real-time molecular characterization of tumors.